Electrostatic image forming processes are known in which an electrostatic latent image contained on the surface of an electrosensitive member is developed by contacting such surface with an electroscopic powder, such electroscopic powder being either dry or dispersed in an insulating carrier liquid, such carrier liquid or dispersant normally having a volume resitivity greater than 10.sup.9 ohm-cm and dielectric constant less than 3. These prior art dry and liquid dispersed toning techniques are well known in electrophotographic office copying machines and the like, in which an electrostatic latent image on a photosensitive recording member is developed on such member, and may be retained on such member or transferred to another sheet, such as a paper web or the like as desired.
The prior art processes have certain inherent disadvantages, in that dry development processes are normally incapable of producing high definition copy due to the relatively coarse nature of the dry toner material, and in addition are incapable of half tone reproduction as normally used in the art. Liquid dispersed toners are able to produce images of superior definition with excellent half tone rendition, but suffer the disadvantage that the copy sheet becomes wetted with dispersant liquid, which is normally removed by the application of heat which introduces solvent vapor into the atmosphere.